A typical vehicle is equipped with an air bag apparatus. An air bag apparatus instantaneously inflates a bag by releasing gas into the bag when the vehicle suddenly decelerates, such as in the event of a collision. The air bag apparatus includes an inflator, which functions to instantaneously release gas, and a bag, which is inflated by the gas released from the inflator to protect a vehicle occupant. The inflator includes an igniter for generating heat, a gas generation composition that burns explosively due to the heat from the igniter in order to generate gas, and an inflator filter for filtering and cooling the generated gas. The inflator filter filters and cools the high-temperature gas, which contains residues.
As such an inflator filter, a filter obtained by compressing and shaping a knit mesh net that is knitted in stockinet or a filter obtained by rolling a flat-woven net into a layered cylinder has been proposed in the prior art. However, such an inflator filter is manufactured by preparing a long net for a plurality of layers and then superimposing the net into layers or rolling the net into layers. Thus, the manufacture of the filter is troublesome.
Accordingly, winding filters are now mainly used as inflator filter members (refer to, for example, Japanese Laid-Open Patent Publication No. 11-348712). A winding filter is obtained by directly knitting a metal wire, which is a deformed wire having a circular or square cross-section, into a cylindrical body having meshes.
The diameter of wire used for such a winding filter tends to be set large to withstand the temperature and pressure of the gas that passes through the filter. Further, the meshes of the filter tend to be set large to reduce pressure loss of the gas that passes through the winding filter. However, when the winding filter with such settings is applied to an air bag apparatus that is designed to generate a large amount of gas, such as an air bag apparatus for a front passenger seat of an automobile, the amount of gas may exceed the capture capability of the filter. As a result, the filter may fail to capture residues contained in the gas.